Vice President Mike Pence greets attendees prior to a National Medal of Arts and National Humanities Medal ceremony in the East Room of the White House, Thursday, Nov. 21, 2019, in Washington. (AP Photo/Steve Helber)

WASHINGTON, DC – They are the ghosts of the House impeachment hearings.

Vice President Mike Pence. Secretary of State Mike Pompeo. Energy Secretary Rick Perry. Acting White House Chief of Staff Mick Mulvaney. Rudy Giuliani. And perhaps most tantalizingly, the mustachioed John Bolton, President Donald Trump’s former national security adviser.

These principals closest to Trump have hovered over the House’s impeachment hearings, only the fourth such presidential inquiry in U.S. history. Often mentioned through five days and a dozen witnesses but absent from the room, they sit at the center of a remarkably consistent story told by others of Trump’s pressure campaign on Ukraine to investigate the Bidens. All the while, military aid to the U.S. ally was withheld as Trump trafficked in a debunked conspiracy theory that Ukraine, and not Russia, meddled in the 2016 election.

British-born Fiona Hill, the nonsense-free Russia scholar who served on the National Security Council, on Thursday lectured the president’s allies for contributing to what she called that “fictional narrative.” And she had some pointed advice for the absentees, who refused to cooperate under orders from the White House.

“I believe that those who have information that the Congress deems relevant have a legal and a moral obligation to provide it,” Hill told the House Intelligence Committee in the capstone hearing to a week of testimony.

It wasn’t clear which of the missing witnesses Hill was referencing or whether Chairman Adam Schiff intended to seek more testimony as Democrats drive to vote on impeachment by year’s end. But in her crisp accent and straightforward style, Hill has made clear that Bolton, her former boss, is one such person with relevant information to the investigation — and there are likely many others.

“Everyone was in the loop,” European Union Ambassador Gordon Sondland testified Wednesday.

Bolton, though, was vexed by Trump’s Ukraine plans.

Hill said that when she complained to Bolton that then-Ambassador Marie Yovanovitch was being “smeared,” Bolton “looked pained, basically indicated with body language that there was nothing which we could do about it,” Hill said Thursday. Then, Bolton “said that Rudy Giuliani was a hand grenade that was going to blow everyone up.”

At another point over the summer, Hill testified, a meeting at the White House with Ukrainian officials was cut short when Sondland said he had an agreement with acting chief of staff Mick Mulvaney that Ukraine’s president would get a meeting with Trump if Ukraine agreed to launch investigations.

According to Hill, Bolton “stiffened” and ended the meeting, later telling Hill to report it to National Security Council lawyers.

“I am not part of whatever drug deal Sondland and Mulvaney are cooking up on this,” Hill said Bolton told her.

Bolton’s name was mentioned more than 50 times during Thursday’s hearing alone, according to the transcript.

As for Mulvaney, a former House member whose name came up a dozen times Thursday: Hill said Sondland reported that Mulvaney had agreed to a White House meeting with the Ukrainians in exchange for an investigation of Burisma. Former Vice President Joe Biden’s son, Hunter, sat on the company’s board.

Pompeo, too, is a former House member. He’s also served as Trump’s CIA director and is considering running for a Senate seat representing Kansas. Sondland said the secretary of state, whose name came up seven times, was among the senior officials well aware of Trump’s pressure campaign on Ukraine.

On Thursday, Hill said she confronted Sondland about pursuing Trump’s agenda and not coordinating with career officials who were trying to support the U.S. ally on the border of Russia. Sondland’s response, according to Hill: “But I'm briefing the president. I'm briefing Chief of Staff Mulvaney. I'm briefing Secretary Pompeo. And I've talked to Ambassador Bolton. Who else do I have to deal with?”

Dubbed one of the “three amigos” pursuing Ukraine policy, Sondland disputed that they were running some sort of “rogue” operation outside official U.S. policy. He produced emails and texts showing he, former special envoy Kurt Volker and Perry kept Pompeo and others apprised of their activity. One message from Volker said, “Spoke w Rudy per guidance from S.” He said, “S means the secretary of state.”

Sondland also said he raised his concerns about a quid pro quo for military aid with Pence — a conversation Pence has said he didn’t recall.

On Thursday, as Schiff recessed the hearing for the final House votes before Thanksgiving, the odds of a late appearance by Bolton or others seemed distant. Bolton has not been subpoenaed by impeachment investigators and his attorney, Charles Cooper, has said he will not come without one. A ruling by a federal judge enforcing a congressional subpoena could give House lawmakers reason to subpoena him, or other figures like Perry or Pompeo.

Rep. Alexandria Ocasio-Cortez said she especially wants to know more about Pence’s role in Ukraine policy.

“At this point it’s not, has Trump has committed a crime, it’s who else has committed a crime,” she said. “If Mike Pence knew or participated in extortion with any government it needs to be looked into.”

But many Democrats say have all the testimony the need. Rep. Elissa Slotkin, the Michigan Democrat who was one of the freshmen with national security backgrounds who pushed Pelosi toward impeachment proceedings, said what matters is keeping the inquiry short and straightforward.

“I’m happy that things are moving at a very fast clip and I think that we shouldn’t let the perfect be the enemy of the good,” she said. “We should be voting on this sooner rather than later.”